The present invention relates to a filter for removing leucocytes from concentrated platelets or platelet-rich plasma.
Platelet transfusion is effective for bleeding patients who show severe sympton due to thrombocytopenia or thrombocytosis. Recently large amount of chemotherapeutics have been used for a treatment of a malignant tumor or a blood dyscrasia and the patients have shown thrombocytopenia after chemotherapies. Therefore platelet transfusions increase in the clinical cases. The patients who produced alloantibodies against HLA antigen show a transfusion reaction by leukocytes intermixed. In such case, the patients can not be administered with the general platelet transfusion but can be administered with HLA compatible platelet transfusion. However, HLA compatible platelet transfusion is not generally conducted because HLA type does not easily match. So, removal of leucocytes is the most effective method to prevent the transfusion reaction.
As a method for removing leucocytes from concentrated platelets or platelet-rich plasma, there are known following methods.
(1) A method wherein a platelet layer is obtained from a buffy coat layer by centrifugal separation for separating blood components.
(2) A method wherein a bag containing collected blood is centrifuged to remove a leucocyte layer.
(3) A method wherein a filter for removing leucocytes is used.
In the methods (1) and (2), leucocytes are removed utilizing the difference in the specific gravity between leucocytes and platelets. However, it is difficult to efficiently remove only leucocytes because the difference in the specific gravity between leucocytes and platelets is small.
In the method (3), concentrated platelets or platelet-rich plasma is filtrated through a filter wherein a fleece or a nonwoven fabric made of an extra fine fiber is filled into a housing. This method is widely available because a high removal rate of leucocytes can be attained with an easy operation. In this case, a filter comprising a filter medium using a fleece of a cotton, a regenerated cellulose or a cellulose acetate is not preferable because of the following reason. The diameter of monofilament of such material is large and therefore a large volume is required for a housing in which a required amount of the fiber is filled. An amount of residual platelets in the housing after filtration becomes large when the large volume housing is used. Therefore, a nonwoven fabric made of an extra fine fiber such as a polyester, whose character as a fiber medium is improved, is used. That is, the nonwoven fabric made of an extra fine fiber can save a volume of a housing, and realizes a high removal rate of leucocytes with lower loss of platelets.
In the method (3), however, there are defects that platelets are lost when a quantity of blood to be filtrated is small and that the removal rate of leucocytes lowers when blood is stored for a long period.
An objects of the present invention is to provide a filter for removing leucocytes which removes leucocytes efficiently from concentrated platelets or platelet-rich plasma without loss of platelets, solving the above mentioned problems.
This and the other objects of the present invention will become apparent from the description hereinafter.